In this paper we present extremely flexible and low power digital binary ASK, PSK, and FSK demodulator architectures for short-range applications that use a limiter amplifier (i.e. high gain comparator) at the front-end. The limiter amplifier can be used at the front-end when the SNR of the received signal is high. This technique converts the analog signal to digital via one bit processing and eliminates mixers, PLL and AGC devices or replaces them with very low power digital counterparts. The rest of circuit is then implemented using digital signal processing (DSP) technique. Detailed system analysis of such demodulators are carried out in this paper. In addition, some new low-size and low-power modulators/demodulators are also described and analyzed for low-power short-range applications.